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Python Kivy self.add_widget() doesn't update while code running

The idea is to create a texting app that works like Messenger. I am having a problem with the chat history which is a "BoxLayer (or GridLayer)" containing all previous text. I want when I insert a new text, it's will appear as a new label or a box and stay below the previous text like this, but when I run the code and insert input text, it's not appearing. I spent hours to find the answer both myself and on the internet, but it's kind of hard for a beginner like me.
.Py file
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.gridlayout import GridLayout
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button
from kivy.uix.label import Label
from kivy.core.image import Image
from kivy.properties import StringProperty
from kivy.core.window import Window
from kivy.graphics.context_instructions import Color
class MainWidget(Widget):
request = StringProperty("This is a previous text, don't mind")
insert_text = StringProperty("Insert Here")
window_size = (305,400)
refresh_key = False
def __init__(self,**kwargs):
super().__init__(**kwargs)
self.Window_Minimum()
def on_size(self,*args):
print(self.width,self.height)
def on_text_validate(self,widget): #<<<<<<<<<<<<<<<<<<<<<<<<<<< input text
request=widget.text
Chat_history_update().chat_history(request)
def Window_Minimum(self):
Window.minimum_width,Window.minimum_height=self.window_size
class Chat_history_update(BoxLayout):
def __init__(self,**kwargs):
super().__init__(**kwargs)
l = Label(text="This is a previous text, don't mind",size_hint=(1, None),height=("30dp"))
self.add_widget(l)
def chat_history(self,request): # <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< Add Label Function
l = Label(text=request, size_hint=(1, None),height=("30dp"))
self.add_widget(l) # <<<<<<<<<<<<< This won't update my app screen
class Assistant(App):
pass
if __name__ == "__main__":
Assistant().run()
Kv file
MainWidget:
<MainWidget>:
BoxLayout:
size: root.size
orientation: "vertical"
GridLayout:
cols: 3
size_hint: 1,None
height: "50dp"
spacing: "10dp"
padding: "10dp"
Label:
text:"Erza Assistant"
Button:
text:"Edit Path"
Button:
text:"Setting"
GridLayout:
size: self.size
rows: 2
spacing: "10dp"
padding: "10dp"
ScrollView: #<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< Here my text display
Chat_history_update:
orientation: "vertical"
size_hint: 1, None
height: self.minimum_height
TextInput:
size_hint: 1, None
height: "40dp"
text: root.insert_text
multiline: False
on_text_validate: root.on_text_validate(self)

Your code:
Chat_history_update().chat_history(request)
is creating a new instance of Chat_history_update, and calling chat_history() for that new instance. That new instance is not part of your GUI, so you will see no effect. The fix is to access the correct instance of Chat_history_update (the one that is in your GUI). To do that, you can add an id in your kv:
ScrollView: #<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< Here my text display
Chat_history_update:
id: chu
orientation: "vertical"
size_hint: 1, None
height: self.minimum_height
And then use that id in your py code:
def on_text_validate(self,widget): #<<<<<<<<<<<<<<<<<<<<<<<<<<< input text
request=widget.text
self.ids.chu.chat_history(request)

I think this here might help. You have to reference widgets in the kivy language by using id or ids.
If you do not yet i strongly suggest you learn how to reference widgets by their ids.

Recup input value through screen manager kivy

I want to catch a value from my first screen into my thirdscreen.
In the first, I write my name in an input field.
I go to the next window.
And I try to show my name in this last window.
So I share the code with you and I hope I will find an issue.
Python code :
import kivy
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.lang import Builder
from kivy.core.window import Window
from kivy.properties import ObjectProperty
from kivy.uix.screenmanager import ScreenManager, Screen
#define ou different screens
class FirstWindow(Screen):
def envoyer(self):
name = self.ids.nom_input.text
self.ids.my_name.text = name
class SecondWindow(Screen):
pass
class ThirdWindow(Screen):
#PROBLEM HERE
def on_press(self):
self.ids.recup_infos.text = self.root.get_screen('FirstWindow').ids.my_name.text
class WindowManager(ScreenManager):
pass
class MonWidget(Widget):
pass
kv = Builder.load_file('new_window.kv')
class AwesomeApp(App):
def build(self):
Window.clearcolor = (0,0,0,0)
return kv
if __name__ == '__main__':
AwesomeApp().run()
My KV CODE :
WindowManager:
FirstWindow:
SecondWindow:
ThirdWindow:
<FirstWindow>:
name: "romain"
BoxLayout:
orientation: "vertical"
size: root.width, root.height
Label:
id: my_name
text: "Entrez votre nom"
font_size: 32
TextInput:
id: nom_input
multiline: False
size_hint: (1, .5)
Button:
text: "Next screen"
font_size: 32
on_press: root.envoyer()
on_release:
app.root.current = "Mickael"
root.manager.transition.direction = "left"
<SecondWindow>:
name: "Mickael"
BoxLayout:
orientation: "vertical"
size: root.width, root.height
Label:
text: "Entre votre ville"
font_size: 32
TextInput:
id: ville_input
multiline: False
size_hint: (1, .5)
Button:
text: "Vérifier les infos"
font_size: 32
on_release:
app.root.current = "foncier"
root.manager.transition.direction = "left"
Button:
text: "go back first screen"
font_size: 32
on_release:
app.root.current = "romain"
root.manager.transition.direction = "right"
<ThirdWindow>:
name: "foncier"
BoxLayout:
orientation: "vertical"
size: root.width, root.height
Label:
text: "Verifier : "
font_size: 32
Label:
id: recup_infos
text: ""
font_size: 32
color: 'white'
Button:
text: "On press"
font_size: 32
#Problem HERE
on_press: root.on_press()
Button:
text: "Précedent"
font_size: 32
on_release:
app.root.current = "Mickael"
root.manager.transition.direction = "right"
Could you help me ?
Thank you
Romain

In your on_press method:
def on_press(self):
self.ids.recup_infos.text = self.root.get_screen('FirstWindow').ids.my_name.text
self.root.get_screen('FirstWindow').ids.my_name.text isn't the correct way to get access to widgets outside of the class that you are in right now, or in this situation, screen. The correct way is to use the App.get_running_app() method:
self.ids.recup_infos.text = App.get_running_app().root.ids.First.ids.my_name.text
But before doing that, you have to give ids to the screens of your app, so that the First argument of the method demonstrated above actually makes sense:
WindowManager:
FirstWindow:
id: First
# "First" is the id of the FirstWindow class
# which can also explain why there was a "First" arg
# inside "App.get_running_app().root.ids.First.ids.my_name.text"
SecondWindow:
id: Second
ThirdWindow:
id: Third
Still confused to why this works? Let's divide the attributes of App.get_running_app().root.ids.First.ids.my_name.text into 3 parts:
App.get_running_app(): this method returns the location of your running App class, in this case AwesomeApp. This also acts as self if you were to get the variable inside the App object itself
.root.ids.First: if you read the Kivy documentation, or just simply watched Kivy course videos online, carefully, you should know that self.root.ids inside the App object returns a list of ids of the widgets inside your root widget. In this case, App.get_running_app().root.ids is doing the same thing here, and your screens are passed in the ScreenManager root widget, hence make First an available attribute in App.get_running_app().root.ids
.ids.my_name.text: same as above, App.get_running_app().root.ids.First acts the same as self if you were to run it in your FirstWindow class, which gives you the opportunity to get access to variables outside of your working classes/screens

How to change a space when a button is pressed with kivy?

I am trying create a GUI by implementing the template of the ComicCreator GUI sample as a template for my own project. The code is easy to follow, but I would like to be able to reconfigure the drawingspace.kv, each time a button is pushed, say for example something like this:
Q: How could I configure the drawingspace.kv to have a different layout with different widgets for each button that is pressed?

A neat way to do this is to use screen.
Since I allready have an example of this app from you earlier question, it was easy to implement the screens, and rewrite the classes a bit.
When a button is pressed, you set the screenmanager's current to whatever the name you named the screen you want.
Then you just edit the layouts as you want inside of each screen, in the kv file, or python file.
I choose to make most of the layout stuff in kv language here. Because I find it easier to develop a layout the way I want it this way.
Later I could rewrite it to python if I want that.
So my python file looks like this now:
from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import StringProperty
from kivy.clock import Clock
from kivy.uix.screenmanager import Screen,ScreenManager,NoTransition
from kivy.lang import Builder
import time
Builder.load_file("kv.kv")
class MyLayout(BoxLayout):
def __init__(self,**kwargs):
super(MyLayout,self).__init__(**kwargs)
self.orientation = "vertical"
self.padding = 10
class MainScreen(Screen):
pass
class RemoveScreen(Screen):
pass
class GroupScreen(Screen):
pass
class MyLogo(BoxLayout):
your_time = StringProperty()
def __init__(self,**kwargs):
super(MyLogo,self).__init__(**kwargs)
Clock.schedule_interval(self.set_time, 0.1)
def set_time(self,dt):
self.your_time = time.strftime("%m/%d/%Y %H:%M")
class MyApp(App):
def __init__(self,**kwargs):
super(MyApp,self).__init__(**kwargs)
self.sm = ScreenManager(transition=NoTransition())
self.sm.add_widget(MainScreen(name = "main"))
self.sm.add_widget(RemoveScreen(name = "remove"))
self.sm.add_widget(GroupScreen(name = "group"))
self.sm.current = "main"
def build(self):
return self.sm
if __name__ == "__main__":
MyApp().run()
And kv.kv file looks like this:
#:kivy 1.9.1
<MyButtons#BoxLayout>:
padding: 10,10,10,0
spacing: 10
size_hint: 1,0.3
orientation: "horizontal"
Button:
text: "Clear"
on_press: app.sm.current = "main"
Button:
text: "Remove"
on_press: app.sm.current = "remove"
Button:
text: "Group"
on_press: app.sm.current = "group"
Button:
text: "Color"
Button:
text: "Gestures"
<MyLogo>:
spacing: 10
padding: 10,10,10,0
orientation: "horizontal"
BoxLayout:
orientation: "vertical"
size_hint: 0.3,1
canvas:
Rectangle:
pos: self.pos
size: self.size
AsyncImage
source: 'http://lmsotfy.com/so.png'
Label:
size_hint: 1,0.3
text: root.your_time
color: [0,0,0,1]
Label:
size_hint: 1,0.3
text: "NYC, New York, USA"
color: [0,0,0,1]
<MainScreen>:
MyLayout:
MyLogo:
#Button:
# text: "main"
MyButtons:
#buttons
BoxLayout:
padding: 10,10,10,10
size_hint: 1,0.3
Button:
text: "Total figures: 1 Kivy Started"
<RemoveScreen>:
MyLayout:
MyLogo:
BoxLayout:
orientation: "horizontal"
Label:
font_size: "40sp"
text: "Remove"
Button:
font_size: "20sp"
text: "Remove this or something"
MyButtons:
#buttons
BoxLayout:
padding: 10,10,10,10
size_hint: 1,0.3
Button:
text: "Total figures: 1 Kivy Started"
<GroupScreen>:
MyLayout:
MyLogo:
BoxLayout:
orientation: "vertical"
Label:
font_size: "40sp"
text: "Group"
Button:
font_size: "20sp"
text: "Something groups stuff"
MyButtons:
#buttons
BoxLayout:
padding: 10,10,10,10
size_hint: 1,0.3
Button:
text: "Total figures: 1 Kivy Started"

The layout frame should be a screen manager, and each layout a screen. Screen transitions would be then triggered by pressing the buttons. You can also watch a tutorial here if you don't know how to do this, but the documentation should be enough.

Kivy - Change screens after pushing button in ModalView

I am having difficulty figuring out how to correctly change screens using the on_press attribute of a button inside of a ModalView widget.
On pressing the button in the ModalView, I want the screen to change to the game_screen_name defined in the Game1HomeScreen class and other GameHomeScreen classes (as is done with the NewGameButton and SavedGameButton below). This app has multiple games, so I would rather not make a call directly to Game1HomeScreen1().game_screen_name and want to instead keep it generic, so game_screen_name takes on the value of the class from which NewGamePopup is called.
What is a good way to do this?
The main.py code:
class Game1HomeScreen(Screen):
game_screen_name = 'game1_gameboard_screen_name'
class NewGamePopup(ModalView):
pass
class GamesApp(App):
sm = ScreenManager()
def show_new_game_popup(self):
p = NewGamePopup()
p.open()
def prev_screen(self):
self.sm.current = self.game_screen_name #this line does not work of course, because there is no game_screen_name variable in the NewGamePopup class.
The .kv code:
<NewGamePopup>:
size_hint: .5, .3
NewGameBoxLayout:
padding: [10,10,10,10]
orientation: 'vertical'
Label:
font_name: 'fonts/playce.ttf'
font_size: '14sp'
markup: True
text: '[color=#000000]Are you sure? Current game will be erased![/color]'
Button:
font_name: 'fonts/playce.ttf'
font_size: '14sp'
text: 'Confirm'
background_normal: 'img/red_button5.png'
background_down: 'img/red_button5.png'
size_hint_y: None
on_press: root.dismiss(); app.prev_screen()
<Game1HomeScreen>:
GeneralBoxLayout:
BannerGridLayout1:
BodyBoxLayout:
rows: 2
Image:
source: 'img/logo.png'
size_hint: (1.0,.9)
GridLayout:
cols: 2
spacing: '5dp'
padding: '5dp'
size_hint: (1.0,.1)
NewGameButton:
id: game1
on_press:
if saved_game1.disabled == False: app.show_new_game_popup()
else: root.manager.current = root.game_screen_name; saved_game1.disabled = False
SavedGameButton:
id: saved_game1
on_press: root.manager.current = root.game_screen_name;
FooterGridLayout:
ReturnButton:
text: 'Return to main menu'
on_press: root.manager.current = 'home'

Save the game screen name in a string property when the game is selected
from kivy.properties import StringProperty
....
class GamesApp(App):
game_screen_name = StringProperty('')
Then you can use the sm.current call later as needed. Too many things were left out of the code snippet in the question to create a working version; even the build method was missing.

How to unbind a property automatically binded in Kivy language?

The Kivy Language automatically creates internal binds in properties. For example, if we assign the position of the parent to the position of the child, then the position of the child is going to be updated automatically:
Widget:
Label:
pos: self.parent.pos
In this case, if we move the parent Widget, then the child is also going to move. How do I unbind the property pos from the child? I know how to unbind (properties)[http://kivy.org/docs/api-kivy.uix.widget.html#using-properties] that I bind myself but how do I unbind them if I don't know the name of the method it is bound.
Here is a small example to show what I mean. The Button Up moves the GridLayout to the top and Down to the Bottom. The Button Center center itself in the middle of the screen. My problem is that when I click Up or Down my Centered button is not anymore.
from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.lang import Builder
Builder.load_string("""
<Example>:
GridLayout:
id: _box
cols: 3
size_hint: .7, .3
pos_hint: {'center_x': .5}
x: 0
Widget:
Button:
pos: self.parent.pos
size: self.parent.size
on_press: _box.y = 0
text: "Down"
Widget:
Button:
pos: self.parent.pos
size: self.parent.size
on_press: self.center_y = root.height/2
text: "Out of the Grid"
Widget:
Button:
pos: self.parent.pos
size: self.parent.size
on_press: _box.top = root.height
text: "Up"
""")
class Example(FloatLayout):
pass
class ExampleApp(App):
def build(self):
return Example()
if __name__ == "__main__":
ExampleApp().run()
Why do I want to do that in any case? I am using an animations on the GridLayout that constantly updates the position. The normal position of the buttons should be inside the gridlayout but once in a while one of the buttons flies over the screen and come back to the same position. The problem is that I cannot make them fly while my gridlayout is also moving because the property is bound and as soon as the button try to fly it goes back to the grid. That also means that the binding is sometimes desirable. What I want is have control of the bind and unbind.

Comments don't seem to be working right now so I'll post this as a answer.
You already have a FloatLayout(your root widget). Use that instead of
creating a new FloatLayout.
Before removing the widget from the grid.
store it's size,
set size_hint to None, None
set pos_hint to position the widget in the center.
When adding the widget to grid do the reverse.
Here's your code with these fixes::
from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.lang import Builder
Builder.load_string("""
<Example>:
center_button: _center_button
center_widget: _center_widget
grid:_grid
GridLayout:
id: _grid
cols: 3
size_hint: .7, .3
pos_hint: {'center_x': .5}
x: 0
Widget:
Button:
pos: self.parent.pos
size: self.parent.size
on_press: _grid.y = 0
text: "Down"
Widget:
id: _center_widget
Button:
id: _center_button
pos: self.parent.pos
size: self.parent.size
on_press: root.centerize(*args)
text: "Out of the Grid"
Widget:
Button:
pos: self.parent.pos
size: self.parent.size
on_press: _grid.top = root.height
text: "Up"
""")
class Example(FloatLayout):
def centerize(self, instance):
if self.center_button.parent == self.center_widget:
_size = self.center_button.size
self.center_widget.remove_widget(self.center_button)
self.center_button.size_hint = (None, None)
self.add_widget(self.center_button)
self.center_button.pos_hint = {'center_x': .5, 'center_y':.5}
else:
self.remove_widget(self.center_button)
self.center_button.size_hint = (1, 1)
self.center_widget.add_widget(self.center_button)
self.center_button.size = self.center_widget.size
self.center_button.pos = self.center_widget.pos
class ExampleApp(App):
def build(self):
return Example()
if __name__ == "__main__":
ExampleApp().run()
Update 1:
If for whatever reason you still need to unbind the properties bound by kvlang you can do so using introspection to get a list of observers for the property. so for your case it would be something like this::
observers = self.center_widget.get_property_observers('pos')
print('list of observers before unbinding: {}'.format(observers))
for observer in observers:
self.center_widget.unbind(pos=observer)
print('list of observers after unbinding: {}'.format(self.center_widget.get_property_observers('pos')))
You would need to use the latest master for this. I should fore-warn you to be extremely careful with this though you'd need to reset the bindings set in kvlanguage, but then you loose the advantage of kv language... Only use this If you really understand what you are doing.

Following #qua-non suggestion, I am temporarily moving the child to another parent. It actually unbinds it, or maybe, rebinds it to the new parent. This is a partial solution because of whatever reason, it doesn't update the position automatically when I took it out of the GridLayout (i.e. when I press enter) and put it into the new parent. I need to press 'Up' (or 'Down') after the 'Out of the Box' button.
However, it does go back immediately. When you click again on the 'Out of the box' button the 2nd time, it goes back to its original position. This part works perfectly. And it continue obeying to its parent instructions.
In other words, it doesn't work immediately when I take out of the grid but it does when I put it back.
from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.lang import Builder
Builder.load_string("""
<Example>:
center_button: _center_button
center_widget: _center_widget
float: _float
grid:_grid
GridLayout:
id: _grid
cols: 3
size_hint: .7, .3
pos_hint: {'center_x': .5}
x: 0
Widget:
Button:
pos: self.parent.pos
size: self.parent.size
on_press: _grid.y = 0
text: "Down"
Widget:
id: _center_widget
Button:
id: _center_button
pos: self.parent.pos
size: self.parent.size
on_press: root.centerize(*args)
text: "Out of the Grid"
Widget:
Button:
pos: self.parent.pos
size: self.parent.size
on_press: _grid.top = root.height
text: "Up"
FloatLayout:
id: _float
size_hint: None,None
""")
class Example(FloatLayout):
def centerize(self, instance):
if self.center_button.parent == self.center_widget:
self.center_widget.remove_widget(self.center_button)
self.float.add_widget(self.center_button)
self.float.size = self.center_button.size
self.float.x = self.center_button.x
self.float.center_y = self.center_y
else:
self.float.remove_widget(self.center_button)
self.center_widget.add_widget(self.center_button)
self.center_button.size = self.center_widget.size
self.center_button.pos = self.center_widget.pos
class ExampleApp(App):
def build(self):
return Example()
if __name__ == "__main__":
ExampleApp().run()

Here is something very similar to what I was trying. The difference is that I ended binding the properties manually so I can unbind them. Basically if I uncomment the line #pos: self.parent.pos of the 'out of the box' button, then I cannot unbind them unless I assign the Button to another parent as #qua-non suggested.
from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.lang import Builder
Builder.load_string("""
<Example>:
center_button: _center_button
GridLayout:
cols: 3
size_hint: .7, .3
pos_hint: {'center_x': .5}
Button:
on_press: self.parent.y = 0
text: "Down"
Widget:
Button:
id: _center_button
size: self.parent.size
#pos: self.parent.pos
on_press: root.centerize(*args)
text: "Out of the Grid"
Button:
on_press: self.parent.top = root.height
text: "Up"
""")
class Example(FloatLayout):
def __init__(self, **kwargs):
super(Example, self).__init__(**kwargs)
self.center_button.parent.bind(pos=self.binder)
self.centered = False
def binder(self, instance, value):
self.center_button.pos = instance.pos
def centerize(self, instance):
if self.centered:
self.center_button.parent.bind(pos=self.binder)
self.center_button.y = self.center_button.parent.y
self.centered = False
else:
self.center_button.parent.unbind(pos=self.binder)
self.center_button.center_y = self.height/2
self.centered = True
class ExampleApp(App):
def build(self):
return Example()
if __name__ == "__main__":
ExampleApp().run()